1. Background
The present invention relates to a transmission quality measurement apparatus which measures the transmission quality of data contained in data packets, for example audio data or video data, received via a network, a transmission quality measurement method which measures transmission quality, and a transmission quality measurement system in which data packets containing, for example, audio data or video data are transmitted from a first transmission quality measurement apparatus to a network, and a second transmission quality measurement apparatus measures the transmission quality of the data contained in the data packets, transmitted from the first transmission quality measurement apparatus, and received from the network.
2. Description of the Related Art
There have hitherto been techniques for monitoring and measuring the transmission quality of audio data or video data when the audio data or video data is packetized and transmitted via a network. For example, Japanese Patent Application Laid-Open No. 2006-268124 has disclosed a technique by which the receiving end of audio data packets or the like estimates the degradation of audio data or the like from the number of overflows or underflows in the reception buffer and thereby measures the transmission quality of audio data or the like sensed by the recipient.
Also, there has been a technique which transmits data packets simulating audio data packets or video data packets from one transmission quality measurement apparatus arranged in an IP (Internet Protocol) network to another transmission quality measurement apparatus. The technique measures the transmission quality of the audio data or video data from properties of packets received by the other transmission quality measurement apparatus.
For audio data, the transmission quality is calculated based on ITU-G.107 being ITU standard (ITU: International Telecommunication Union) or JJ-201.01 being TTC standard (TTC: Telecommunication Technology Committee); for video data, the transmission quality is calculated based on ITU-T.241 (ITU-R BT.1720).
However, according to the conventional art which measures transmission quality between transmission quality measurement apparatuses, transmission quality or packet loss cannot be measured when packets are routed through an analog network.
That is, as illustrated in FIG. 12, when data packets transmitted from one transmission quality measurement apparatus are relayed from an IP network through an analog network to an IP network, the data packets are converted into an analog signal in the analog network and then packetized again in the IP network and received by another transmission quality measurement apparatus. However, the received data packets are not necessarily identical to the data packets prior to going through the analog network; thus, according to the conventional art which compares transmitted data packets with received data packets on a packet by packet basis, the transmission quality of audio data or video data cannot be accurately measured.
Also, for data packets which are packetized again in the IP network after going through the analog network and received by the other transmission quality measurement apparatus, sequence numbers attached to each packet may be lost or the order of sequence numbers may be changed; thus, according to the conventional art which measures packet loss based on the sequence number, packet loss may not be detected.
There also arises a problem that, since the received data packets are not necessarily identical to the data packets prior to going through the analog network, it is not possible to measure fluctuations which represent enlarged interval between each audio data contained in the received packets or enlarged audio data component contained in the received packets.
In view of the above problems of the conventional art, the present invention advantageously provides a transmission quality measurement apparatus, transmission quality measurement method and transmission quality measurement system which can measure the transmission quality or packet loss of audio data or video data even when audio data or video data is relayed as data packets from an IP network through an analog network to an IP network.